Interaction between network services and intelligent network services for controlling rerouting of a call

ABSTRACT

Rerouting, as specified by ITU-T Q.730 is a network service that is executed by and under control of switching nodes, whereas IN services are executed under the control of a service control entity and invoked for certain calls only. Because of the two levels of control that are also separate from each other, inconsistencies may occur when an IN service is invoked for a call that may be in addition subject to rerouting. This problem is solved-in that a service control entity is adapted to perform the steps of receiving information relating to the rerouting of the call from the service switching entity, selecting a rerouting procedure for the call according to the received information, and sending an instruction to the service switching entity to continue the call according to the rerouting procedure. The information relating to the rerouting of the call information is in particular information about a rerouting capability of a preceding switching node.

TECHNICAL FIELD

The present invention relates to telecommunications networks, inparticular to methods and devices for controlling a rerouting of a callin an Intelligent Network.

BACKGROUND

In a telecommunications network a call initiated by a calling entity toa called entity is routed through a number of switching nodes before itreaches its destination. An example of how a call may be routed from acalling entity to a called entity in a telecommunications network isgiven with reference to FIG. 1 a. A calling entity CE100 sets up a callto a called entity CE105 by sending a call set up request to a switchingnode 101. The switching node 101 receives the call set up request andanalyses the destination number comprised therein, which is typically anumber associated to the user of called entity CE105. Depending on theoutcome of the analysis the switching node 101 will select the mostappropriate next switching node for routing the call further in the mostefficient way, thereby using as few as possible switching nodes in thecall path to the destination. The switching node 101 selects a switchingnode 102. Switching nodes 102 and 103 behave in a similar way and routethe call further towards switching node 104, which is closest to thecalled entity CE105. Accordingly a call path is established from thecalling entity CE100 to the called entity CE105 with a call pathdirection as depicted. In general, a call path is a sequence ofswitching nodes that are subsequently involved in the routing of a callbetween a calling entity and a called entity. A call path direction isdefined to be the course on which the call is being routed or is aimedto be routed, starting at the calling entity and ending at the calledentity. Switching nodes 102 and 103 are sometimes also referred to astransit switching nodes, because they function as transits betweenswitching nodes 101 and 104. The switching node 104 then connects theincoming call to called entity CE105 and a speech connection may beopened.

Rerouting, also referred to as Pivot Routing or Redirection, is anotherrouting mechanism that has been specified for example in ITUTelecommunication Standardization Sector (ITU-T) recommendation Q.370(12/1999). Rerouting can be used to set up a call to a furtherdestination, other than the called entity. The further destination forthe purpose of rerouting will be referred to as the reroutingdestination entity in the remainder. The switching node in the call paththat decides to reroute the call may also be referred to as the invokingnode. Depending on the rerouting destination entity, the invoking nodemay request either a succeeding node in the call path direction to thecalled entity to reroute the call to the rerouting destination entity,or a preceding node. Such a node should support rerouting, that is, hasthe capability to perform the rerouting. A switching node that has thecapability to reroute a call is also referred to as a rerouting node inliterature. A switching node may have the capabilities to act as eitheror both an invoking node and a rerouting node.

An example of rerouting is given with reference to FIG. 1 b. Depictedare main switching nodes 107 to 110 that co-operate when rerouting of acall is required. A switching node 107 propagates a call towards adestination number associated to a called entity CE111, as received froma calling entity CE106. Since the switching node 107 in this examplesupports rerouting, i.e. has the capability to perform rerouting, ifrequested by an invoking node, it indicates so to the next switchingnode. The switching node 107 may include for example a dedicatedparameter comprising a rerouting indicator in a call set up message, forexample the Initial Addressing Message (IAM) as specified in theIntegrated Services Digital Network (ISDN) User Part (ISUP) call controlprotocol.

During the call set up process the call may transit through one or more(transit) switching nodes 108, similar to the example of FIG. 1 a. Anyswitching node 108 will pass the rerouting indicator as received fromthe switching node 107 transparently. The decision that rerouting has tobe invoked is taken at a switching node 109 acting as the invoking nodein this example. The switching node 109 also determines the reroutingdestination entity RDE112. Since the call set up message indicates thatrerouting can be performed by a preceding switching node in the callpath direction, viz. the switching node 107, the switching node 109requests the preceding switching node 108 in the call path direction topropagate the call back towards the switching node 107 (i.e. opposite tothe call path direction to the called party CE111), indicated by thedashed arrow. The switching node 107 then reroutes the call to thererouting destination entity RDE112. The call may transit via furthertransit switching nodes between the switching node 107 and the reroutingdestination RDE112, not depicted. All network resources, i.e. the one ormore transit switching nodes 108 between the switching node 107 and theinvoking node 109 are released and can be used for new calls.

In addition to so-called network services such as rerouting, i.e.services executed by and under the control of switching nodes, there arealso Intelligent Network services that are executed and controlled by anIntelligent Network (IN). According to the IN concept, serviceintelligence or service logic is separated from switching functions.This separation basically enables network operators to develop anddeploy services and features independently of vendors, allowing moreflexibility in service development, simplified rollout, reduced costsand greater autonomy. Examples of IN protocols are the IntelligentNetwork Application Protocol (INAP), the Advanced IN (AIN), and theCustomized Applications for Mobile network Enhanced Logic (CAMEL). INAPwas developed for fixed line networks and is the primary protocol usedfor fixed line IN outside of North America. AIN is a variant developedfor North America.

CAMEL is a Global System for Mobile communications (GSM) Phase 2+ andWideband Code Division Multiple Access (WCDMA) network feature specifiedin 3GPP TS 22.078. CAMEL is based on core INAP with modifications totake into account, amongst others, subscriber mobility. In particular,CAMEL enables the use of operator-specific services by a subscriber evenwhen roaming outside the subscriber's Home Public Land Mobile Network(PLMN). A CAMEL-based Intelligent Network comprises as main entities aservice switching entity for switching tasks, also referred to as SSF(Service Switching Function) or gsmSSF (GSM Service Switching Function)and a service control entity comprising the service intelligence orlogic also referred to as SCF (Service Control Function) or gsmSCF (GSMService Control Function).

Rerouting, as stated before, is a network service that is executed byand under control of switching nodes, whereas IN services are executedunder the control of a service control entity and invoked for certaincalls only. Because of the two levels of control that are also separatefrom each other, inconsistencies may occur when an IN service is invokedfor a call that may be in addition subject to rerouting. For example, acall may be rerouted by a switching node to a rerouting destinationentity, that according to the service logic of an IN service is on abarred list, resulting in inconsistent or undesirable service behavior.Furthermore, the service control entity may apply rerouting itself nothaving knowledge of rerouting capabilities of switching nodes. This maylead to unnecessary occupation of network resources and reroutingfailures.

SUMMARY

It is therefore an object of the invention to provide methods, devices,and computer programs that overcome the aforementioned problems andimprove rerouting of a call in a telecommunications network.

This object is achieved by the methods as described in claims 1 and 11.Furthermore, the invention is embodied in a service control entity and aservice switching entity according to claims 26 and 27, respectively,and computer programs according to claims 28 and 29, respectively, and acomputer-readable medium product according to claim 30. Advantageousembodiments are described in the further claims.

A method for controlling a rerouting of a call from a called entity to arerouting destination entity in a telecommunications network isdescribed. The telecommunications network comprises a service controlentity, a service switching entity and a switching node. The switchingnode precedes the service switching entity in a call path direction froma calling entity to the called entity.

The service control entity receives information relating to thererouting of the call from the service switching entity, selects arerouting procedure for the call according to the received informationand sends an instruction to the service switching entity to continue thecall according to the rerouting procedure.

The service switching entity receives information relating to thererouting of the call. The service switching entity sends theinformation relating to the rerouting of the call to the service controlentity. Then the service switching entity receives an instruction fromthe service control entity to continue the call according to a reroutingprocedure selected by the service control entity. In response toreceiving the instruction, the service switching entity continues thecall according to the instruction received.

The invention provides for a control of a rerouting of a call by aservice control entity. According to the invention, the service controlentity receives information relating to the rerouting of the call from aservice switching entity, e.g. information about a rerouting capabilityof a preceding switching node, or an indication that rerouting isinvoked by a switching node. Based on the received information andaccording to its internal service logic using a rerouting procedure forthe call according to the received information together with thecapability to send out a corresponding instruction, the service controlentity is fully empowered to control the rerouting of the call. Theservice control entity may determine how to continue the rerouting of acall when initiated at a switching node of the network, or may decidethat the rerouting is allowed or not, or to be modified beside manyother options. The instruction to the switching entity effecting thatthe switching entity continues the call according to the instruction,extends the control over rerouting to further entities of the networklike switching nodes. Therefore, inconsistencies in the handling of arerouting caused by a probable double invocation of a rerouting for onecall by both the network and IN can be avoided. Furthermore, theextension of control over rerouting in the network effects an efficientrerouting and avoids unnecessary occupation of network resources andrerouting failures.

The invention furthermore concerns a service control entity and serviceswitching entity. It also concerns a computer program loadable into aprocessing unit of a service control entity and a computer programloadable into a processing unit of a service switching entity to performany of the steps of the aforementioned methods when operated at therespective device.

The computer program can be stored on a computer readable medium. Thecomputer-readable medium can be a permanent or rewritable memory withinthe service control entity or the service switching entity or locatedexternally. The computer program can be also transferred to the servicecontrol entity or the service switching entity for example via a cableor a wireless link as a sequence of signals.

In the following, detailed embodiments of the present invention shall bedescribed in order to give the skilled person a full and completeunderstanding. However, these embodiments are illustrative and notintended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a schematic illustration of a telecommunications networkfor routing of a call according to the prior art.

FIG. 1 b shows a schematic illustration of a telecommunications networkfor rerouting of a call according to the prior art.

FIG. 2 a shows a schematic illustration of a telecommunications networkaccording to a first embodiment of the invention.

FIG. 2 b shows a schematic illustration of a telecommunications networkaccording to a second embodiment of the invention.

FIG. 2 c shows a schematic illustration of a telecommunications networkaccording to a third embodiment of the invention.

FIG. 3 a shows a sequence diagram depicting messages exchanged in atelecommunication network in an exemplary embodiment of the inventionexecuted at call set up.

FIG. 3 b shows a sequence diagram depicting messages exchanged in atelecommunication network in an exemplary embodiment of the inventionexecuted after initiation of rerouting at an invoking node.

FIG. 4 shows a flow diagram of method steps performed by a servicecontrol entity.

FIG. 5 shows a flow diagram of method steps performed by a serviceswitching entity.

FIG. 6 shows a block diagram of an embodiment of a service controlentity.

FIG. 7 shows a block diagram of an embodiment of a service switchingentity.

DETAILED DESCRIPTION

FIG. 2 a depicts a schematic overview of a telecommunications networkcomprising an Intelligent Network for a call subject to rerouting.

The Intelligent Network comprises a service control entity 201 and aservice switching entity 202. Furthermore, switching nodes 203, 204 and205 are depicted, each of which may be a Mobile Switching Centre (MSC).The switching node 203 may function as a rerouting node; the switchingnode 204 may be a transit switching node and the switching node 205 maybe an invoking node. Further, a calling entity CE200, a called entityCE206 and a rerouting destination entity RDE207 are depicted.

Intelligent Networks services are executed by and under the control ofthe service control entity 201. The service control entity 201 is ableto communicate with the service switching entity 202 using anIntelligent Network protocol such as CAMEL or INAP. The serviceswitching entity 202 is preferably co-located at a transit switchingnode 204, but may also be co-located at any of the other types ofswitching nodes for the purpose of rerouting, such as an invoking nodeor a rerouting node, as is explained with reference to FIGS. 2 b and 2c. Alternatively, the service switching entity 202 may be implemented asa separate node.

According to the embodiment depicted in FIG. 2 a, a call from thecalling entity CE200 to the called entity CE206 may be rerouted to thererouting destination entity RDE207, whereby the switching node 205 actsas the invoking node. The switching node 205 propagates the call back(i.e. opposite to the call path direction), indicated by the dashedarrows, via the switching node 204 and the service switching entity 202to the switching node 203 that acts as the rerouting node in thisembodiment. Hence, according to FIG. 2 a, the service switching entity202 is located at the switching node 204 acting as a transit switchingnode for the purpose of rerouting.

According to the embodiment depicted in FIG. 2 b, the switching node 204acts as the invoking node of a rerouting of a call from the calledentity CE206 towards the rerouting destination entity RDE207. In orderto reroute the call, the switching node 204 requests the precedingswitching node 203 in the call path direction to reroute the call to thererouting destination entity RDE207, indicated by the dashed arrow. Inthis embodiment, the service switching entity 202 is co-located at theswitching node 204 acting as the invoking node.

FIG. 2 c depicts a further embodiment wherein the switching node 205acts as an invoking node and the switching node 204 as a rerouting node.Similar to the previous embodiments, the switching node 205 requests thepreceding switching node 204 in the call path direction to reroute thecall to the rerouting destination entity RDE207, indicated by the dashedarrow. Hence, in this embodiment, the service switching entity 202 isco-located at the switching node 204 acting as the rerouting node.

The involvement of the service switching entity 202 and the servicecontrol entity 201 in the rerouting of the call is explained withreference to FIGS. 3 a and 3 b.

FIG. 3 a depicts a sequence diagram showing messages exchanged in atelecommunication network at call set up. Depicted are switching nodes320, 321 and 324, a service switching entity 322 and a service controlentity 323. The switching node 320 is capable to act as a rerouting nodeand precedes the switching node 321 in a call path direction from acalling entity (not depicted in FIG. 3 a) to a called entity (notdepicted in FIG. 3 a). The calling entity, if depicted, would bepreceding the switching node 320 and the called entity, if depicted,would be succeeding the switching node 324. The service switching entity322 may be co-located at the switching node 321. The service switchingentity 322 communicates to other switching nodes via the switching node321. Hence, the switching node 321 can both be a preceding node and asucceeding node to the service switching entity 322 in the call pathdirection, because it can act both as a sender and a receiver to theservice switching entity 322 in the same call path direction. Otherwise,the switching node 321 may be omitted from the sequence diagram becauseits further function is merely a transit node to the service switchingentity. The service control entity 323 comprises service logic forexecuting Intelligent Network services and is able to communicate withthe service switching entity 322. Furthermore, there is depicted theswitching node 324 succeeding the service switching entity 322 in thecall path direction. The call path of a call from the calling entity tothe called entity may be formed sequentially by switching nodes 320,321, service switching entity 322, switching nodes 321 and 324. Theswitching node 324 may act as a further rerouting node or as an invokingnode for the purpose of rerouting.

During the handling of a call set up, the switching node 320 receives instep 300 a call set up message originating from the calling entity, to afirst destination number associated to a user of the called entity. Thismessage may be an IAM in case of call control protocol ISUP. Anyswitching node that is capable to act as a rerouting node, i.e. supportsthe rerouting of the call, should indicate this to the next switchingnode in the call path direction, which is in accordance withstandardized rerouting mechanisms. In step 301 the switching node 320signals its rerouting capability, e.g. by including an indication of thererouting capability in the call set up message, towards the switchingnode 321. The switching node 321 sends the call set up message includingthe rerouting information indicating the rerouting capability of theswitching node 320, to the service switching entity 322. The switchingnode 321 may also add to the call set up message an indication of itsown rerouting capability or replace the indication of the reroutingcapability of the switching node 320 by the indication of its ownrerouting capability. The service switching entity 322 sends thererouting information comprising the indication of the reroutingcapability to the service control entity 323 in step 303, preferably ina dedicated information element in an initial message, preferably aCAMEL Initial Detection Point message. The service control entity 323 isthus provided with an indication whether a preceding switching nodesupports rerouting. Now, the service control entity is able to select arerouting procedure for the call taking knowledge about one or morererouting capabilities of one or more preceding switching nodes intoaccount.

The usage of an initial message provides that the service control entity323 is informed about rerouting capabilities of one or more precedingswitching nodes in the network at an initial stage of the call. Itallows the service control entity 323 to take control of the processingof the call at an early stage, preferably even before any rerouting hasactually been invoked. The information element is preferably dedicated,i.e. pre-defined values may be used for indication of a reroutingcapability at pre-defined positions within the initial message with thepre-definitions known to both the service control entity 323 and theservice switching entity 322. A common notation with pre-defined valuesand a pre-defined position of the information element in the initialmessage eases the insertion and extraction of a value for both theservice switching and service control entity. The initial message andthe dedicated information element are preferably standardized althoughproprietary extensions may be used if standardization is not possible.

Typically, the service switching entity 322 sends the reroutinginformation indicating the rerouting capability unchanged to the servicecontrol entity 323, but it is also possible that the reroutinginformation is modified by the service switching entity 322 beforesending it to the service control entity 323, e.g. the information maybe reformatted by the service switching entity 322 for integrity orreadability purposes, or the content may be changed, or new informationmay be added. A modification of the rerouting information hence canincrease the flexibility of the method. The service control entity 323comprises service logic for determining how to respond to the reroutinginformation and selects a rerouting procedure accordingly in step 304.In particular, the rerouting procedure may comprise a reroutingpermission related to a switching node. A rerouting permission mayrelate to an allowance or not-allowance for the rerouting of a call.

An instruction in accordance with the rerouting permission which is sentfrom the service control entity 323 to the service switching entity 322,instructs the service switching entity 322 to continue the callaccording to the rerouting procedure comprising the reroutingpermission. Hence, a defined permission status can be introduced underthe control of the service control entity 323 at the service switchingentity 322 and hence within the network as a whole, thus furtherminimizing any inconsistencies in rerouting.

In step 305 the service control entity 323 sends an instruction to theservice switching entity 322 in accordance with the selected reroutingprocedure. The instruction may be sent in a CAMEL ContinueWithArgumentmessage, in a CAMEL Connect, or in a CAMEL Request Report BCSM (BasicCall State Model) message.

Several alternatives to the call set up process may be performeddepending on the rerouting procedure selected.

In a first embodiment the rerouting procedure may comprise a reroutingpermission indicating that any invocation of rerouting by a succeedingswitching node is to be suppressed. Accordingly, the service controlentity 323 is enabled to give priority to a rerouting invoked accordingto an IN service, thereby preventing any undesirable effects caused bytwo invocations of a rerouting for one call. The service control entity323 may decide to suppress the invocation of a subsequent rerouting,based on subscription information of the calling or the called entity.The service control entity 323 instructs the service switching entity322 in step 305 accordingly. The instruction may be sent in a CAMELContinueWithArgument or CAMEL Connect message, comprising an indicationthat a subsequent invocation of rerouting is to be suppressed. Step 306of arming a detection point for rerouting is not performed in thisembodiment.

In response to the instruction from the service control entity 323, theservice switching entity 322 may send a message towards the followingswitching node 324, via switching node 321, to indicate that anysubsequent rerouting is to be suppressed in steps 307 and 308. Forexample, the service switching entity 322 may delete or change thererouting information comprised in the call set up message, beforesending the call set up message towards the following switching node324, via switching node 321. By deleting or changing the reroutinginformation the service switching entity 322 can inform the succeedingswitching nodes that rerouting is to be suppressed for the call.

The rerouting procedure may prescribe in a further embodiment that anysubsequent invocation of rerouting is allowed, provided that the servicecontrol entity 323 is informed upon invocation of the rerouting. Anotification about an invocation of rerouting occurring subsequently inthe call allows the service control entity 323 to control the laterinvocation of the rerouting, for example it may screen the reroutingdestination entity and possibly decide to block rerouting after all. Theservice switching entity 322 receives an instruction from the servicecontrol entity 323 in step 305 indicating that the service controlentity 323 requires a notification when rerouting is invokedsubsequently in the call. The instruction may be sent in a CAMEL RequestReport BCSM message, comprising an indication that the service switchingentity 322 should initiate a process for detecting an invocation ofrerouting.

Subsequently the service switching entity 322 may arm a detection pointaccording to the basic call state model (BCSM) in step 306, fordetecting the event that rerouting is invoked by a switching nodesucceeding the service switching entity 322 in the call path direction.This allows the service switching entity 322 to be notified whenrerouting is invoked by a succeeding node and to report that event tothe service control entity 323. In step 307 the service switching entity322 may inform the next switching node 321 in a message, e.g. a call setup message, to continue the call set up process without changing thererouting information as received from the preceding switching node 320.

In yet another embodiment, the rerouting procedure may comprise arerouting permission indicating that rerouting is allowed, but should beperformed by a switching node succeeding the service switching entity322 in the call path direction from the calling entity to the firstcalled entity, i.e. on the outgoing side of the service switching entity322. This has the effect that the dialogue between the service controlentity 323 and the service switching entity 322 can be maintained duringthe actual rerouting of the call. Hence, the service control entity 323may remain in the call until the actual rerouting to the reroutingdestination entity is performed, and is enabled to send furtherinstructions. The service control entity 323 sends an instruction to theservice switching entity 322 accordingly in step 305, preferably in aCAMEL ContinueWithArgument message comprising an indication thatrerouting is allowed to be performed by a succeeding switching node orin a CAMEL Continue message.

The service switching entity 322 may respond by informing the nextswitching node 321 in a message, e.g. a call set up message, to continuethe call set up process and including an indication that any of the nextswitching nodes 321 or 324 is allowed to perform rerouting.

In a further embodiment the rerouting procedure may specify thatrerouting is allowed without any involvement of the service controlentity 323. According to this embodiment, the service control entity maydecide at an early stage of the call that it does not need to beinformed of a possible subsequent rerouting invoked by the network.Hence, the service switching entity 322 is not required to initiate anymonitoring on the invocation of a rerouting. Also, the dialogue betweenthe service control entity 323 and the service switching entity 322 canbe terminated, which saves network resources. The service control entity323 may instruct the service switching entity 322 in step 305accordingly. The instruction may be sent in a CAMEL ContinueWithArgumentmessage comprising an indication that rerouting is allowed or in a CAMELContinue message. The service switching entity 322 may instruct thefollowing switching node 321 in a message, e.g. a call set up message,to continue the call set up process and thereby leaving the reroutinginformation received from the switching node 320 unchanged. According tothis embodiment any subsequently invoked rerouting may result in thecall being rerouted to the rerouting destination entity by any of thepreceding or succeeding switching nodes or by the service switchingentity 322 itself.

In FIG. 3 b detailed operation of an embodiment of the invention isdepicted that occurs after rerouting of the call is invoked. In thisembodiment it is possible, but not necessary, that earlier in the callset up process the service control entity 323 has requested to beinformed when rerouting is invoked, for example as described withreference to FIG. 3 a. Accordingly the service switching entity 322 mayhave armed a detection point for detecting the invocation of rerouting.

A switching node 324 may decide that rerouting is to be invoked and maydetermine the new destination of the call, i.e. the reroutingdestination entity (not depicted in FIG. 3 b). The switching node 324thus behaves as an invoking node as explained above. Subsequently, theswitching node 324 may send a request in opposite direction of the callpath direction to perform rerouting in step 311. The request may be anISUP release message comprising an indication of the reroutingdestination entity and comprising further rerouting information such asthe cause of the rerouting invocation which is laid down in a causecode.

As soon as the service switching entity 322 receives a notification ofthe request in step 312 via the switching node 321, it sends anindication of the invocation of the rerouting at the switching node 324to the service control entity 323 in step 313. In addition, the serviceswitching entity 322 may also send the indication of the reroutingdestination entity to the service control entity 323. The serviceswitching entity 322 may also inform the service control entity 323 ofthe cause code and possibly of other relevant rerouting information thatis sent along with the request for rerouting by the switching node 324.Because the service control entity 323 receives the indication of theinvocation of the rerouting from the service switching entity 322 earlyafter the invocation of the rerouting, it is able to take control of thererouting in time before the rerouting has actually become effective.The service control entity 323 may for example allow or forbid thererouting. Since the service control entity 323 is also informed aboutthe rerouting destination entity, it may check whether the reroutingdestination entity is on a barred list and take appropriate action.

The indication of the invocation of rerouting, the indication of thererouting destination entity and any other rerouting information such asthe cause code may be sent to the service control entity 323 preferablyin one or more dedicated information elements in a CAMEL Event ReportBasic Call State Model (Event Report BCSM) message.

The service control entity 323 comprises service logic for analyzing thereceived rerouting information and for determining how to respond to thereceived rerouting information, and selects a rerouting procedureaccordingly in step 314. In particular, the rerouting procedure maycomprise a rerouting permission related to a switching node. A reroutingpermission may relate to an allowance or not-allowance for the reroutingof a call.

In step 315 the service control entity 323 sends an instruction to theservice switching entity 322 in accordance with the selected reroutingprocedure.

Depending on the rerouting procedure selected several alternatives tothe call rerouting process may be performed.

In a first embodiment, the service control entity 323 may select in step314 a rerouting procedure comprising a rerouting permission indicatingthat rerouting to the rerouting destination entity is allowed and thatthe service control entity 323 requires to remain in the call. Accordingto this embodiment it is assumed that earlier in the call, the servicecontrol entity 323 had received an indication from the service switchingentity 322 that the service switching entity 322 is prepared to perform,in cooperation with a preceding switching node 321, the rerouting of thecall, not depicted. The indication may be sent from the serviceswitching entity 322 to the service control entity 323 in a CAMEL EventReport BCSM message, including e.g. a busy event detection point and arerouting-pending indication. The presence of the rerouting-pendingindication in the CAMEL Event Report BCSM message informs the servicecontrol entity 323 that the service switching entity 322 is prepared toperform rerouting to a rerouting destination entity. An indication ofthe rerouting destination entity is included in the rerouting-pendingindication.

The service switching entity 322 is instructed by the service controlentity 323 in step 315, for example by means of a CAMEL Request ReportBCSM message followed by a CAMEL Continue message. Because the serviceswitching entity 322 had sent a rerouting-pending indication to theservice control entity 323, the sending of the CAMEL Request Report BCSMmessage prior to the sending of the CAMEL Continue message has theeffect that the dialogue between the service control entity 323 and theservice switching entity 322 remains active.

In response to the instruction from the service control entity 323, theservice switching entity 322 may send a message, e.g. a call set upmessage, comprising the rerouting destination entity to a precedingswitching node 321 indicating that the call is to be set up to saidrerouting destination entity in step 316. The switching node 321 may, inresponse to the aforementioned message from the service switching entity322, set up the call to the rerouting destination entity.

In another embodiment, the rerouting procedure selected in step 314 maycomprise a rerouting permission indicating that rerouting to thererouting destination entity is allowed and that the service controlentity 323 does not require to remain in the call. According to thisembodiment, the service control entity may decide e.g. based on theindication of the rerouting destination entity, that rerouting cancontinue without involvement of the Intelligent Network. Hence, thedialogue between the service control entity 323 and the serviceswitching entity 322 can be terminated, which saves network resources.Accordingly, the service control entity 323 sends an appropriateinstruction to the service switching entity 322 in step 315, for examplea CAMEL Continue message or a CAMEL ContinueWithArgument message. Thelatter one may be used if the service control entity 323 may want toreplace the original cause code, as received from the invoking node 324,by a new cause code.

The service switching entity 322 may subsequently propagate the ISUPrelease message that it received from the switching node 324, further inopposite direction of the call path direction in step 316. The ISUPrelease message comprises the indication of the rerouting destinationentity and an indication that the call is allowed to be rerouted to thererouting destination entity by any of the preceding switching nodes 321or 320. The dialogue between the service control entity 323 and serviceswitching entity 322 is terminated. The call is rerouted to thererouting destination entity by the preceding switching nodes 321 and320.

According to a further embodiment, the service control entity 323 mayselect a rerouting procedure prescribing that the rerouting destinationentity e.g. is not approved and prescribing to reroute the call to amodified rerouting destination entity in step 314. Hence, the servicecontrol entity 323 is able to change the rerouting of the call withrespect to the rerouting destination in accordance with internalsubscription information. The possibility to reroute to a modifieddestination entity can thus provide for an increase in flexibility whichis beneficial among other advantages, like increase in security (e.g.for an untrusted rerouting destination entity) and/or an increase ofrerouting success (e.g. due to an unavailability of a reroutingdestination entity).

The service control entity 323 sends in step 315 an instruction to theservice switching entity 322, preferably a CAMEL Connect messagecomprising an indication of the modified rerouting destination entity.In response to the CAMEL Connect message from the service control entity323, the service switching entity 322 may send a message, e.g. a callset up message, comprising the indication of the modified reroutingdestination entity to the switching node 321 indicating that the call isto be set up to said modified rerouting destination entity in step 316.

The service control entity 323 may alternatively send a CAMELContinueWithArgument message or a CAMEL Release Call message, eachcomprising an indication of the modified rerouting destination entity.In response to either of these messages, the service switching entity322 may propagate the ISUP release message to the switching node 321 instep 316, whereby the ISUP release message comprises the indication ofthe modified rerouting destination entity and an indication that thecall is allowed to be rerouted to the modified rerouting destinationentity by any of the preceding switching nodes 321 or 320. In responseto the ISUP release message, the switching nodes 321 or 320 may reroutethe call to the modified rerouting destination entity.

In yet another embodiment, the rerouting procedure selected in step 314comprises a rerouting permission indicating that the reroutingdestination is not approved and rerouting is not allowed. In step 315the service control entity 323 instructs the service switching entity322 accordingly, preferably in a CAMEL ContinueWithArgument message,including an indication that the call is not allowed to be rerouted. Theservice switching entity 322 subsequently sends a message to thepreceding switching node 321 comprising the indication that the call isnot allowed to be rerouted. Alternatively, the service control entity323 may send a CAMEL Release Call message. In response, the serviceswitching entity 322 may send the ISUP release message that was receivedfrom the switching node 324, to switching node 321 after having removedthe rerouting information contained therein. As a result the call willbe released and hence no rerouting is effected. This embodiment isparticularly advantageous when the service control entity 323 invokes atthis stage of the call an IN rerouting service, having priority over thererouting as invoked by the switching node 324. Now, the reroutinginvoked by the switching node 324 is terminated and inconsistenciescaused by double invocation of rerouting are avoided.

FIG. 4 depicts the steps performed by a service control entity accordingto an embodiment of the invention.

The method according to FIG. 4 may start when a service switching entitysends an initial message, for example a CAMEL Initial Detection Pointmessage, comprising a rerouting indicator originating from a precedingswitching node in a call path direction from the calling entity and thecalled entity. Alternatively, the method of FIG. 4 may be triggered by aservice switching entity sending an event report indicating thatrerouting has been invoked by a succeeding switching node in the callpath direction.

The service control entity performs the step of receiving reroutinginformation in step 401. Said information may be obtained from theinitial message, e.g. by extracting data relating to said informationfrom said message, or from an event report notifying the service controlentity of the invocation of rerouting and comprising an indication of arerouting destination entity, or both.

The method may proceed further to step 402 wherein a rerouting procedurefor the call by the service control entity is selected. Service logic ofthe service control entity may analyze the obtained informationcomprising the rerouting indicator or the rerouting cause code and theindication of the rerouting destination entity.

According to step 403, an instruction is sent from the service controlentity to the service switching entity to continue the call according tothe selected rerouting procedure.

The method may end here or may continue with any of the steps describedherein.

FIG. 5 shows the steps performed by a service switching entity accordingto an embodiment of the invention.

The method according to FIG. 5 may start when a switching node precedingthe service switching entity in the call path direction from a callingentity to a called entity, passes on a call set up message to theservice switching entity comprising an indication that the switchingnode may perform rerouting and hence may act as a rerouting node.Alternatively, the method may start when an invoking node succeeding theservice switching entity in the call path direction sends a request toperform rerouting to a rerouting destination entity and the serviceswitching entity receives an indication of the request.

According to step 501 the service switching entity may perform the stepof receiving rerouting information from the preceding switching node,whereby the rerouting information comprises a rerouting indicator.Alternatively, the service switching entity may receive reroutinginformation comprising an indication of the rerouting destination entityfrom the invoking node after rerouting has been invoked by said invokingnode.

Subsequently, the service switching entity performs the step of sendingthe rerouting information to a service control entity in step 502. Inthe case that the service switching entity received the reroutinginformation from the preceding switching node it may send the reroutinginformation to the service control entity in an initial message,preferably a CAMEL Initial Detection Point (IDP) message, comprising adedicated information element for the rerouting information. In thealternative case, the switching entity sends the rerouting informationfrom the invoking node in an event report to the service control entity.The event report may comprise the indication of the reroutingdestination entity and any relevant rerouting information such as thecause code as received from the invoking node. In both cases above, theservice switching entity may modify the rerouting information beforesending it to the service control entity.

According to step 503 the service switching entity performs the step ofreceiving an instruction from the service control entity. Theinstruction may be received in a CAMEL Connect, Release Call, RequestReport BCSM, Continue or a ContinueWithArgument message, depending onthe type of instruction.

The method may proceed further to step 504 wherein the service switchingentity performs the step of executing the instruction, that is,continuing the call according to the instruction received.

The method may end here or may continue with any of the steps describedherein.

The invention is furthermore embodied in devices which are described inmore detail below in relation to FIG. 6 and FIG. 7. Reference signs areused for illustration only and are not intended to be limiting.

FIG. 6 depicts an embodiment of a service control entity SCE6 comprisinga receiving unit RU6 for receiving messages, a transmitting unit TU6 fortransmitting messages, a processing unit PU6 for processing messages andinformation, and preferably a storage unit SU6 for storing and/orobtaining of stored information.

A service control entity may be a stand alone device. However, it isalso conceivable that a service control entity is operating at aswitching node, e.g. as a hardware and/or software sub-unit of theswitching node. The service control entity may be installed and operatedat the switching node sharing none of the units RU6, TU6, PU6, SU6 withthe switching node or sharing at least one of the units RU6, TU6, PU6,SU6 with units of a switching node. An alternative embodiment is aservice control entity according to a computer program loaded into theprocessing unit of a switching node.

The processing unit PU6 may be adapted to process information relatingto the rerouting of the call received via the receiving unit RU6 from aservice switching entity. Furthermore, the processing unit PU6 may beadapted to select a rerouting procedure for the call according to thereceived information, and to initiate a transmission via thetransmission unit TU6 of an instruction to the service switching entityto continue the call according to the selected rerouting procedure.

According to a preferred embodiment, the processing unit PU6 may beadapted to process information relating to the rerouting of the call.The information relating to the rerouting of the call may comprise anindication whether a switching node preceding the service switchingentity in the call path direction from a calling entity to the calledentity, supports rerouting of the call.

Preferably, the information relating to the rerouting of the call isreceived at the receiving unit RU6 in an initial message comprising adedicated information element for indicating the information relating tothe rerouting of the call. The processing unit PU6 may be adapted toprocess this information. In particular, the processing unit PU6 may beadapted to extract the information from the message and to obtaininformation relating to the rerouting of the call from the extractedinformation based on which the selection of the rerouting procedure canbe executed.

The processing unit PU6 may be further adapted to select a reroutingprocedure that prescribes that the service control entity receives anotification when rerouting is invoked subsequently in the call, e.g.during the call set up process. The processing unit PU6 may be adaptedto initiate a sending, via the transmission unit TU6, of an instructionfor instructing the service switching entity according to the selectedrerouting procedure.

Alternatively or in addition, the processing unit PU6 may be adapted toselect a rerouting procedure that comprises a rerouting permissionrelating to a switching node. In one embodiment the rerouting permissionmay comprise an indication that the call is allowed to be rerouted by aswitching node that succeeds the service switching entity in the callpath direction of the call. The processing unit PU6 may be furtheradapted to initiate a transmission to the service switching entity, viathe transmission unit TU6, of an instruction according to the selectedrerouting procedure, i.e. an instruction indicating the reroutingpermission comprising an indication the call is allowed to be reroutedby a succeeding switching node.

According to another preferred embodiment, the rerouting permission maycomprise an indication that the call is not allowed to be rerouted. Theprocessing unit PU6 may be further adapted to initiate a sending, viathe transmission unit TU6, of an instruction for instructing the serviceswitching entity according to the selected rerouting procedure, i.e. aninstruction indicating a rerouting permission comprising an indicationthat the call is not allowed to be rerouted.

Furthermore, the receiving unit RU6 may be adapted to receiveinformation relating to the rerouting of the call comprising anindication of the invocation of the rerouting of the call at a furtherswitching node that succeeds the service switching entity in the callpath direction from the calling entity to the called entity. Inaddition, the receiving unit RU6 may be adapted to receive informationrelating to the rerouting of the call comprising an indication of thererouting destination entity. Preferably, the receiving unit RU6 may beadapted to receive the information relating to the rerouting of the callin a message, preferably a CAMEL event report message, comprising adedicated information element for the indication of the invocation ofthe rerouting of the call and/or a dedicated information element for theindication of the rerouting destination entity. The processing unit PU6may be adapted to process this information. In particular the processingunit PU6 may be adapted to extract the information from the message andto obtain the indication of the invocation of the rerouting and/or toobtain the indication of the rerouting destination entity.

According to another preferred embodiment, the processing unit PU6 maybe adapted to select a rerouting procedure comprising a reroutingpermission indicating that the call to the indicated reroutingdestination entity is allowed.

The processing unit PU6 may be adapted to initiate a transmission to theservice switching entity, via the transmission unit TU6, of aninstruction according to the selected rerouting procedure.

Alternatively, the processing unit PU6 may be adapted to select arerouting procedure that prescribes to reroute the call to a modifiedrerouting destination entity. In addition, the processing unit PU6 mayfurther be adapted to initiate a sending, via the transmission unit TU6,of an instruction for instructing the service switching entity accordingto the selected rerouting procedure.

FIG. 7 depicts an embodiment of a service switching entity SSE7comprising an input unit IU7, an output unit OU7, a processing unit PU7for processing messages and information, and preferably a storage unitSU7 for storing and/or obtaining of information.

A service switching entity may be a stand alone device and input unitIU7 and output unit OU7 being external interfaces like a receiving unitfor receiving messages and a transmission unit for transmittingmessages, respectively. Preferably, a service switching entity isoperating at a switching node, e.g. as a hardware and/or softwaresub-unit of the switching node. The service switching entity may beinstalled and operated at the switching node sharing none of the unitsIU7, OU7, PU7, SU7 with the switching node or sharing at least one ofthe units IU7, OU7, PU7, SU7 with units of a switching node comprising areceiving unit for receiving messages, a transmission unit for sendingmessages, a processing unit for processing messages and information, andpreferably a storage unit. A preferred embodiment is a service switchingentity according to a computer program loaded into the processing unitof a switching node.

The processing unit PU7 may be adapted to process information relatingto the rerouting of the call received via the input unit IU7 and to sendthe information relating to the rerouting of the call to a servicecontrol entity via output unit OU7. Furthermore, the processing unit PU7may be adapted to process an instruction from the service control entityreceived via the input unit IU7, instructing the service switchingentity to continue the call according to a rerouting procedure selectedby the service control entity, and to continue the call according to theinstruction received.

According to a preferred embodiment, the input unit IU7 may be adaptedto receive information relating to the rerouting of the call comprisingan indication whether a switching node preceding the service switchingentity in the call path direction supports rerouting of the call. Theprocessing unit PU7 may be adapted to process this information.

The processing unit PU7 may be further adapted to initiate sending ofthe information relating to the rerouting of the call via the outputunit OU7 to the service control entity in an initial message comprisinga dedicated information element for indicating the information relatingto the rerouting of the call. The processing unit PU7 may have modifiedthe information before initiating to send it to the service controlentity.

According to another preferred embodiment, the input unit IU7 is adaptedto receive an instruction from the service control entity in response tothe sending of the information relating to the rerouting of the call tothe service control entity. The instruction may comprise an indicationthat the service control entity requires a notification when reroutingis invoked subsequently in the call. In addition, the processing unitPU7 may be adapted to process the instruction and to initiate aprocedure for detecting invocation of rerouting. Preferably, theprocessing unit PU7 may initiate arming of a detection point in the BCSMfor detecting invocation of rerouting.

Alternatively or in addition, the instruction from the service controlentity comprises an indication of a rerouting permission related to aswitching node. The rerouting permission may indicate that the call isallowed to be rerouted by a switching node that succeeds the serviceswitching entity in the call path direction, after invocation ofrerouting has taken place. Additionally, the processing unit PU7 may beadapted to process the instruction and to initiate the sending of amessage, e.g. call set up message, to the succeeding switching node viathe output unit OU7, whereby the message comprises an indication thatthe call is allowed to be rerouted by the succeeding switching node.

In a further preferred embodiment, the input unit IU7 is adapted toreceive an instruction comprising a rerouting permission indication thatthe call is not allowed to be rerouted, in the event of a laterinvocation of rerouting during the call. Additionally, the processingunit PU7 may be adapted to process the instruction and to initiatesending a message, e.g. a call set up message, via the output unit OU7,to the succeeding switching node, whereby the message comprises anindication that the call is not allowed to be rerouted by the succeedingswitching node.

Furthermore, the input unit IU7 may be adapted to receive informationrelating to the rerouting of the call comprising an indication of theinvocation of the rerouting of the call at a further switching node thatsucceeds the service switching entity in the call path direction. Inaddition, the input unit IU7 may be adapted to receive informationrelating to the rerouting of the call comprising an indication of thererouting destination entity. Preferably, the processing unit PU7 may beadapted to process this information. In particular, the processing unitPU7 may be adapted to extract the information from a message wherein itis received and to obtain the indication of the invocation of thererouting and/or to obtain the indication of the rerouting destinationentity. Additionally, the processing unit PU7 may be adapted to initiatethe sending of the information via the output unit OU7 to the servicecontrol entity. In a preferred embodiment, the processing unit PU7 maybe adapted to initiate the sending of the information in a message,preferably a CAMEL event report message, comprising a dedicatedinformation element for indicating the invocation of the rerouting ofthe call and/or a dedicated information element for indicating thererouting destination. The processing unit PU7 may have modified theinformation before initiate the sending to the service control entity.

According to an alternative embodiment, the input unit IU7 is adapted toreceive an instruction comprising a rerouting permission indicatingwhether or not the call is allowed to be rerouted to the reroutingdestination entity. Additionally, the processing unit PU7 may be adaptedto process the instruction.

If the instruction comprises a rerouting permission indication that thecall is allowed to be rerouted to the rerouting destination entity, theprocessing unit PU7 may be further adapted to initiate sending amessage, e.g. a call set up message, via the output unit OU7, to thepreceding switching node, or to initiate sending a call release message,via the output unit OU7, to the preceding switching node, whereby thecall release message comprises the rerouting destination and anindication that the call is allowed to be rerouted by the precedingswitching node.

Alternatively, if the instruction comprises a rerouting permissionindication that the call is not allowed to be rerouted to the reroutingdestination entity, the processing unit PU7 may be further adapted toinitiate sending a message, e.g. a call release message, via the outputunit OU7, to the preceding switching node, whereby the message comprisesan indication that the call is not allowed to be rerouted by thepreceding switching node.

The input unit IU7 may be further adapted to receive an instructioncomprising an indication that the call is to be rerouted to a modifiedrerouting destination entity. In addition, the processing unit PU7 maybe adapted to process the instruction and to initiate sending a message,e.g. a call set up message, via the output unit OU7, to the precedingswitching node, whereby the message comprises an indication of themodified rerouting destination entity. Alternatively, the processingunit PU7 may initiate sending a call release message, via the outputunit OU7, to the preceding switching node, whereby the call releasemessage comprises an indication of the modified rerouting destinationentity and an indication that the call is allowed to be rerouted by thepreceding switching node.

IN protocols like INAP and CAMEL Application Part (CAP, e.g. CAPv4, see3GPP TS 29.078 and 3GPP TS 23.078) are preferably amended by at leastone of the following detailed enhancements to provide a serviceswitching entity and a service control entity with the capabilitiesaccording to the invention:

-   -   a) A new information element (IE) may be added to the “Initial        Detection Point” (InitialDP or IDP in short) message for        indicating to the service control entity that a preceding        switching node may perform rerouting:

Information Element name Description Rerouting/Pivot Indicator This IEindicates whether a preceding switching node supports rerouting.

-   -   -   The IDP comprising the new information element may be used            by the service switching entity to send the information            relating to the rerouting of the call to the service control            entity. For example, the information relating to the            rerouting of the call comprises an indication that a            preceding switching node supports rerouting. The            Rerouting/Pivot Indicator in the IDP is used to carry this            information to the service control entity.

    -   b) The messages “ContinueWithArgument” (CWA) and “Connect” (CON)        may be used to carry information regarding the instruction for        the rerouting procedure to be followed by the service switching        entity. A new “Rerouting/Pivot indicator” information element        (IE) may be added to the “ContinueWithArgument” and to the        “Connect” for this purpose. Also, a new information element for        the indication of the rerouting destination entity may be added        to the “ContinueWithArgument” and the “Connect” to inform the        service switching entity thereof.

Information Element name Description Rerouting/Pivot Indicator This IEindicates to the service switching entity whether rerouting is: to besuppressed, prior to invocation of rerouting; or after invocation ofrerouting: allowed; or allowed on the outgoing side of the serviceswitching entity, i.e. by a succeeding node in the call path direction;or not allowed Rerouting Destination This IE comprises the reroutingIndicator destination entity indicated by the rerouting invoking node orthe service control entity

-   -   -   The “ContinueWithArgument” or the “Connect” message            comprising the new Rerouting/Pivot Indicator may be used by            the service control entity to send an instruction to the            service switching entity to continue the call to according            to the rerouting procedure selected by the service control            entity. For example, to instruct the service switching            entity that rerouting to an earlier indicated rerouting            destination entity is not allowed (or any other kind of            permission). Accordingly the Rerouting/Pivot Indicator            comprises a value that indicates to the service switching            entity that rerouting is not allowed (or any other kind of            permission relating to rerouting).

    -   c) The indication of the rerouting destination entity may be        added to the “Event Report BSCM” message, event report message        in short, when the corresponding Event Type BCSM IE contains        Route Select Failure, or a busy event.

Information Element name Description Rerouting Destination IndicatorThis IE comprises the rerouting destination entity indicated by thererouting invoking node

-   -   -   An event report message comprising the new information            element may be used by the service switching entity to send            the information relating to the rerouting of the call to the            service control entity. For example, the information            relating to the rerouting of the call comprises an            indication of the invocation of a rerouting to a rerouting            destination entity at a switching node, succeeding the            switching node in the call path direction, together with an            indication of the rerouting destination entity. The new            Rerouting Destination Indicator is used to carry the            indication of the rerouting destination entity to the            service control entity.

    -   d) The message “Release Call” (REL) may be used to carry        information regarding the instruction for the rerouting        procedure to be followed by the switching entity. A new        “Rerouting Destination Indicator” information element (IE) may        be added to the “Release Call” for this purpose:

Information Element name Description Rerouting Destination IndicatorThis IE indicates the rerouting destination entity to which the serviceswitching entity should reroute the call.

-   -   -   The service control entity may use the adapted “Release            Call” message to send an instruction to the service            switching entity to continue the call according to the            rerouting procedure selected by the service control entity.            For example, to instruct the service switching entity that            the call is to be rerouted to a modified destination entity.            The new Rerouting Destination Indicator is used to carry the            indication of the modified destination entity to the service            switching entity.

It is apparent that the invention may be implemented in anytelecommunication network like a GSM, Code Division Multiple Access(CDMA), Time Division Multiple Access (TDMA), Universal MobileTelecommunication System (UMTS), or 4G network. A service control entityis typically embodied in a single device or may be distributed overseveral devices. The corresponding applies to a service switchingentity. A service control entity and a service switching entity may beimplemented as separate functions on the same device or platform.

1. A method for controlling a rerouting of a call from a called entityto a rerouting destination entity in a telecommunications networkcomprising a service control entity, a service switching entity and aswitching node preceding the service switching entity in a call pathdirection from a calling entity to the called entity, wherein theservice control entity performs the steps of: receiving informationrelating to the rerouting of the call from the service switching entityin a message comprising a dedicated information element, comprising anindication of the rerouting destination entity, indicating invocation ofrerouting of the call at a further switching node succeeding the serviceswitching entity in the cell path direction, selecting a reroutingprocedure for the call according to the received information, andsending an instruction to the service switching entity to continue thecall according to the rerouting procedure.
 2. The method according toclaim 1, wherein the information relating to the rerouting of the callcomprises an indication whether the switching node supports thererouting of the call.
 3. The method according to claim 1, wherein theinformation relating to the rerouting of the call is received in aninitial message comprising a dedicated information element forindicating the information relating to the rerouting of the call.
 4. Themethod according to claim 1, wherein the rerouting procedure prescribesthat the service control entity requires a notification when reroutingis invoked subsequently in the call.
 5. The method according to claim 1,wherein the rerouting procedure comprises a rerouting permissionrelating to a switching node.
 6. The method according to claim 5,wherein the rerouting permission comprises an indication that the callis allowed to be rerouted by a switching node succeeding the serviceswitching entity in the call path direction.
 7. The method according toclaim 1, wherein the rerouting procedure prescribes to reroute the callto a modified rerouting destination entity.
 8. A method for controllinga rerouting of a call from a called entity to a rerouting destinationentity in a telecommunications network comprising a service controlentity, a service switching entity and a switching node preceding theservice switching entity in a call path direction from a calling entityto the called entity, wherein the service switching entity performs thesteps of: receiving information, relating to the rerouting of the call,comprising an invocation of the rerouting of the call at a furtherswitching node succeeding the service switching entity in the call pathdirection and sent to the service control entity in a message comprisinga dedicated information element for the invocation of the rerouting ofthe call, sending the information relating to the rerouting of the callto the service control entity, receiving an instruction from the servicecontrol entity to continue the call according to a rerouting procedureselected by the service control entity, and continue the call accordingto the instruction received.
 9. The method according to claim 8, whereinthe information relating to the rerouting of the call is received fromthe switching node preceding the service switching entity in the callpath direction and wherein the information comprises an indicationwhether the switching node supports rerouting of the call.
 10. Themethod according to claim 8 wherein the information relating to thererouting of the call is sent to the service control entity in aninitial message comprising a dedicated information element forindicating the information relating to the rerouting of the call. 11.The method according to claim 8, wherein the information relating to thererouting of the call is modified by the service switching entity beforesending it to the service control entity.
 12. The method according toclaim 8, wherein the instruction comprises an indication that theservice control entity requires a notification when rerouting is invokedsubsequently in the call and wherein the service switching entityinitiates a procedure for detecting invocation of rerouting.
 13. Themethod according to claim 8, wherein the instruction comprises anindication of a rerouting permission related to a switching node. 14.The method according to claim 13, wherein the rerouting permissionindicates that the call is allowed to be rerouted by a switching nodesucceeding the service switching entity in the call path direction andwherein the service switching entity sends a message to the succeedingswitching node, whereby the message comprises an indication that thecall is allowed to be rerouted by the succeeding switching node.
 15. Themethod according to claim 13, wherein the rerouting permission indicatesthat the call is allowed to be rerouted to the rerouting destinationentity and wherein the service switching entity sends a messagecomprising the indication of the rerouting destination entity to thepreceding switching node.
 16. The method according to claim 15, whereinthe message further comprises the indication that the call is allowed tobe rerouted by the preceding switching node.
 17. The method according toclaim 13, wherein the rerouting permission indicates that the call isnot allowed to be rerouted and wherein the service switching entitysends a message to the preceding switching node comprising theindication that the call is not allowed to be rerouted.
 18. The methodaccording to claim 8, wherein the information relating to the reroutingof the call comprises an indication of the rerouting destination entity.19. The method according to claim 8, wherein the information relating tothe rerouting of the call is modified by the service switching entitybefore sending it to the service control entity.
 20. The methodaccording to claim 8, wherein the instruction comprises an indication toreroute the call to a modified rerouting destination entity and whereinthe service switching entity sends a message comprising an indication ofthe modified rerouting destination entity to the preceding switchingnode.
 21. A service control entity for controlling a rerouting of a callfrom a called entity to a rerouting destination entity in atelecommunications network comprising a service control entity, aservice switching entity and a switching node preceding the serviceswitching entity in a call path direction from a calling entity to thecased entity, wherein the service control entity comprises: receivingmeans for receiving information relating to the rerouting of the callfrom the service switching entity entity in a message comprising adedicated information element, comprising an indication of the reroutingdestination entity, indicating invocation of rerouting of the call at afurther switching node succeeding the service switching entity in thecall path direction, selection means for selecting a rerouting procedurefor the call according to the received information, and transmissionmeans for sending an instruction to the service switching entity tocontinue the call according to the rerouting procedure.
 22. The servicecontrol entity according to claim 21, wherein the information relatingto the rerouting of the call comprises an indication whether theswitching node supports the rerouting of the can.
 23. The servicecontrol entity according to claim 21, wherein the information relatingto the rerouting of the call is received in an initial messagecomprising a dedicated information element for indicating theinformation relating to the rerouting of the call.
 24. The methodaccording to claim 21, wherein the rerouting procedure prescribes thatthe service control entity requires a notification when rerouting isinvoked subsequently in the call.
 25. The method according to claim 21,wherein the rerouting procedure comprises a rerouting permissionrelating to a switching node.
 26. A service switching entity forcontrolling a rerouting of a call from a called entity to a reroutingdestination entity in a telecommunications network comprising a servicecontrol entity, a service switching entity and a switching nodepreceding the service switching entity in a call path direction from acalling entity to the called entity, the service switching entitycomprising: receiver means for receiving information relating to thererouting of the call, comprising an invocation of the rerouting of thecall at a further switching node succeeding the service switching entityin the call path direction and sent to the service control entity in amessage comprising a dedicated information element for the invocation ofthe rerouting of the call, transmission means for sending theinformation relating to the rerouting of the call to the service controlentity, the receiver means for receiving an instruction from the servicecontrol entity to continue the call according to a rerouting procedureselected by the service control, and means for continuing the callaccording to the instruction received.
 27. The method according to claim26, wherein the information relating to the rerouting of the call isreceived from the switching node preceding the service switching entityin the call path direction and wherein the information comprises anindication whether the switching node supports rerouting of the call.28. The service switching entity according to claim 26, wherein theinformation relating to the rerouting of the call is sent to the servicecontrol entity in an initial message comprising a dedicated informationelement for indicating the information relating to the rerouting of thecall.
 29. The service switching entity according to claim 26, whereinthe information relating to the rerouting of the call is modified by theservice switching entity before sending it to the service controlentity.
 30. The service switching entity according to claim 26, whereinthe instruction comprises an indication that the service control entityrequires a notification when rerouting is invoked subsequently in thecall and wherein the service switching entity initiates a procedure fordetecting invocation of rerouting.